What is the initial management strategy for patients with hypertrophic cardiomyopathy?

Initial Management Strategy for Hypertrophic Cardiomyopathy

For patients with hypertrophic cardiomyopathy (HCM), nonvasodilating beta blockers are the first-line treatment, titrated to effectiveness or maximally tolerated doses, for symptoms attributable to left ventricular outflow tract obstruction (LVOTO). 1

Diagnosis and Classification

Before initiating treatment, it's essential to determine:

• Presence of LVOTO (gradient ≥30 mm Hg at rest or with provocation)
• Symptom status (dyspnea, chest pain, syncope, palpitations)
• Ventricular function (preserved vs. reduced)

Management Algorithm for Symptomatic Obstructive HCM

First-Line Therapy

1. Nonvasodilating beta blockers

   • Target: Resting heart rate <60-65 bpm
   • Titrate to maximally tolerated dose for symptom control
   • Monitor for bradycardia, hypotension, fatigue

2. If beta blockers are ineffective or not tolerated:

   • Switch to nondihydropyridine calcium channel blockers (verapamil or diltiazem) 1, 2
   • Start verapamil at 40 mg TID (max 480 mg daily) 2
   • CAUTION: Verapamil is potentially harmful in patients with severe dyspnea at rest, hypotension, very high resting gradients (>100 mm Hg), and in children <6 weeks of age 1

Second-Line Therapy (for persistent symptoms)

For patients with persistent symptoms despite first-line therapy:

• Add myosin inhibitor (adult patients only) OR
• Add disopyramide (in combination with an atrioventricular nodal blocking agent) OR
• Refer for septal reduction therapy (SRT) at experienced centers 1

Important Medication Considerations

• Discontinue vasodilators (ACE inhibitors, ARBs, dihydropyridine calcium channel blockers) and digoxin as they can worsen LVOTO 1, 2
• Use diuretics cautiously - only low-dose oral diuretics for persistent dyspnea with clinical evidence of volume overload 1
• For acute hypotension, use intravenous phenylephrine (or other vasoconstrictors without inotropic activity), alone or in combination with beta-blocking drugs 1

Management of Non-Obstructive HCM

• Beta blockers or calcium channel blockers for symptom control
• For younger patients (≤45 years) with nonobstructive HCM due to pathogenic cardiac sarcomere genetic variant and mild phenotype, valsartan may be beneficial to slow adverse cardiac remodeling 1

Monitoring and Follow-up

• Regular assessment of symptom status
• Periodic echocardiography to evaluate LVOTO and ventricular function
• ECG monitoring for arrhythmias
• Assessment of medication side effects and tolerance 2

Common Pitfalls to Avoid

1. Inappropriate use of vasodilators: Dihydropyridine calcium channel blockers (e.g., nifedipine), ACE inhibitors, ARBs, and nitrates can worsen LVOTO and should be avoided 1, 2

2. Excessive diuresis: Can decrease preload and augment LVOTO 1

3. Using verapamil in high-risk patients: Verapamil should be avoided in patients with severe dyspnea at rest, hypotension, or very high resting gradients (>100 mm Hg) due to risk of pulmonary edema 1, 3

4. Inadequate beta blockade: Failure of beta blockade should not be declared until demonstrated physiologic evidence of beta blockade (suppression of resting heart rate) is observed 1

5. Combining calcium channel blockers with beta blockers: This combination should be used with caution due to potential for high-grade atrioventricular block 1, 2

The management of HCM has evolved significantly in recent years, with the introduction of cardiac myosin inhibitors like mavacamten providing additional options for patients with persistent symptoms. However, the foundation of initial management remains nonvasodilating beta blockers, with careful attention to symptom control and hemodynamic parameters.